I just picked up a 1990 Cutlass Calais with the 2.5... It was my great aunt's car who quit driving (she is 91). It has 132,000 on it, my cousin (who was in charge of work done on car) told me the bottom end had been redone, but not the head. Upon replacing the valve cover gasket this confirmed that (lots of deposits). He bought the car off someone else recently though so the history is a bit sketchy. The engine sounds noisy, but they all did. I was thinking of using of PZ Longlife 15W40? It's a $350 car, so I don't want to get crazy. What oils do these things like?